#二分法求函数的零点
def cal(x):
    return pow(x,5)-15*pow(x,4)+85*pow(x,3)-225*pow(x,2)+274*x-121

num = int(input());precision = pow(10,-num)
low = 1.5;high = 2.4
while True:
    mid = low + (high - low)/2
    ret = cal(mid)
    if abs(ret) < precision:break
    midhigh = cal(high);midlow = cal(low)
    if abs(midhigh) < abs(midlow):low = mid
    else: high = mid
print("%.6f"%(mid))
